mechanic with a stumper

Ok i got a 99 GMC sierra 2500 with a 6.0 getting codes 141 O2 sensor 2 bank 2 heater malfunction and 158 circuit high and I've checked the wiring for a short and replaced the bank 2 sensor 2 with a new one and I am still getting code 158 after changing the sensor.....any ideas? Has anyone ran into this and fixed it? I'm starting to think it is a PCM problem mabey needs to be flashed or some other driveability issue is forcing the codes to be thrown back. not sure but it is driving me crazy and could use some guidance. Thanx in advance

Disconnect the O2 sensor; the signal voltage should go 0.45 volts. ( This checks the signal line back to the PCM for a short to heater power and an open circuit). Check voltage at the sensor during normal idle . The readings should respond to changes in fuel mixture that last for several seconds.

Hope this helps.

well the o2 is hardwired cause it has been replaced before but will that still work with key on engine off if i backprobe it? which color is the signal wire? if my memory serves it is grey coming off the truck. And any ideas if no short

According to my wiring diagram it is the purple wire for B2S2.
If the sensor is hard wired then someone used a non-OE sensor, one with out the connector, ?
We have not had any luck with non-OE type sensors. If the wires were not soldered into the wiring harnes you could be getting excess resistance in the circuit.

Hope this helps